Nancy Drew arrives at the Wickford Castle Ski Resort in
Wisconsin intending to take a ski vacation, but is snowed in by a blizzard. The castle was originally owned by a millionaire who had
Marie Antoinette’s tower from the Château Rochemont in France taken apart and rebuilt into Wickford Castle, but the entrance is hidden and sealed off. The hotel's caretaker, Dexter Egan, tells Nancy that the hotel's library (also imported from France) has been vandalized, and that the room of a guest named Beatrice Hotchkiss has been robbed. Nancy decides to investigate the crimes. She meets Hotchkiss, a professor of French history specializing in Marie Antoinette; Jacques Bruneis, a former Olympian for France who moved to Wisconsin for his American girlfriend and now works at the resort as a ski instructor; and Lisa Ostrum, a photojournalist documenting old Midwestern mansions. Nancy does chores for Dexter while exploring the hotel and getting to know the other occupants. She finds ID cards from several different states that appear to belong to Lisa, but all have different names on them. She confronts Lisa, who explains that she sometimes needs "alternate identities" as a journalist. Nancy sneaks into the library, which is off-limits as a crime scene. In looking through its contents she finds out that Dexter is the adopted son of the castle's original owner, a prominent local tycoon, and that he got into trouble in his youth: he was expelled from school as a boy, stole money from his father's wallet, and spent twenty-five years in prison after being arrested for check forgery as a young man. Dexter was subsequently disinherited from Wickford Castle and his father's estate. Nancy catches Jacques attempting to saw through a closed gate in a hotel corridor in an effort to reach the locked Marie Antoinette tower. He tells Nancy he is trying to find an old French document that would bring glory to his country, to make up for his poor showing at the Olympics; his great-grandfather had helped ship the tower from France. Nancy agrees to help Jacques find the document, but while searching for clues in Jacques' locker, she is knocked unconscious by an unknown assailant. After waking up in her room, Nancy continues the investigation. She talks to Hotchkiss, who says that one of her goals as a historian is to prove that Marie Antoinette is misunderstood by the general public and was actually a kind, benevolent person. Later, Dexter tells Nancy where the key to the tower is located, saying she has earned the right to explore it. In the tower, Nancy finds puzzles guarding an apparent treasure. The clues to solving these puzzles lead her outside, where someone locks her out of the castle in an attempt to let her die of
hypothermia. She starts up the ski lift to get the attention of Dexter, who helps her back inside. Back in the tower, Nancy finds an old journal belonging to Marie Antoinette. She has Hotchkiss translate it, and discovers that Marie Antoinette hid a large diamond in the tower. Nancy returns to the tower and finds the diamond; she is confronted by Lisa, who has followed her and intends to steal the diamond for herself. Lisa admits to vandalizing the library and robbing Hotchkiss's room, in addition to knocking Nancy unconscious and locking her outside the castle. Nancy apprehends Lisa, and Lisa gets arrested for grand theft. The diamond and the journal are sent to a museum in Paris, and Hotchkiss is granted the rights to publish the journal's English translation in the US. Jacques' family name is cleared, Dexter is asked to be a co-owner of the castle, and Nancy enjoys the rest of her ski vacation. ==Development==